Justina, inspections can vary. It just depends on what you want done. Do you want a whole home inspection like structural, plumbing, electrical etc.? Do you also want a termite inspection? What about a Radon Inspection? Like Maureen stated private inspectors are not licensed in the state of Michigan. Look for one you are comfortable with. You might want to not just ask how much they charge, but what their experience is. (Sometimes cost has to do with the size of the house as well.)
No matter what I would get one you are comfortable with. I am not as excited about the certifications as Maureen shared. I had a major problem with an inspector last year that was a member of one of those groups.
I hope this information helps!